Device for a body&#39;s spherical motion control

ABSTRACT

A device for a body&#39;s ( 1 ) spherical motion control connected with a frame ( 5 ) by means of a spherical joint ( 2 ) arranged on a shank connecting the body ( 1 ) with the frame ( 5 ) and through actuating arms ( 3 ) with drives ( 4 ), where the shank is sectional and the spherical joint ( 2 ) is arranged between the first part ( 9 ) of the shank which is firmly fixed to the frame ( 5 ) and the second part ( 10 ) of the shank which is firmly fixed to the body ( 1 ), whereas the number of parallel arms ( 3 ) with drives ( 4 ) is redundant. In order to increase the accuracy of both the self-calibration itself and a follow-up positioning of the body in the work area and to achieve a large range of the body&#39;s ( 1 ) rotating, the number of parallel arms ( 3 ) with drives ( 4 ) is five at minimum and the length of the first part of the shank ( 9 ) connected to the frame ( 5 ) is longer than the distance of the body ( 1 ) edge from the point of connection of the shank ( 10 ) to the body ( 1 ).

TECHNICAL FIELD

The invention involves a device for a spherical movement of a bodyconnected with a frame through a spherical rule joint aligned on theshank connecting a body with a frame and with a help of control armswith drives.

STATE-OF-THE-ART

The controlled spherical motion of a body is important in manyapplications, for example for tilting heads of machining devices ortelescopes and antennas adjusting. Such a movement is realized todayeither through mechanisms with a series kinematics structure, mostlybased on gymbal or mechanisms with a parallel kinematic structure.Mechanisms with a series kinematics structure have a large moveability,thereupon a range of 180° in two rotations, but they are mass, theirdynamic capabilities are low and they do not allow a continuous movementfrom one position to another in all the positions. On the other hand,mechanisms with a parallel kinematic structure have a limitedmoveability, thereupon a range less than 180° in two rotations usually,but they feature substantially lower weight, have higher dynamiccapabilities and they enable a continuous movement from all positions toall of the subsequent positions.

Tilting heads of machining devices were successfully solved with thehelp of parallel kinematic structures in PCT WO 00/25976 patent forSprint Z3 tilting head made by DS Technologie company where the abilityto move continuously between all the positions with a higher dynamicswas achieved. Singular positions do not allow a larger angle range atthese mechanisms. The improvement of this state-of-the-art is possibleto be achieved through application of redundant (excessive) number ofarms with drives, the number of which is higher than the number ofdegrees of freedom. Such a mechanism with a parallel kinematic structurefor the spherical kinematics is described in an article by Kurtz, R.,Hayward, V.: Multiple-Goal Kinematic Optimization of a ParallelSpherical Mechanism with Actuator Redundancy, IEEE Transactions onRobotics and Automation, 8 (1992), 5, pp. 644-651 where there are 4parallel arms used for a motion of a platform fixed to a frame with aspherical joint on a shank extended from the frame. This solutionenables to increase a range of achievable angle positions substantiallybut it does not allow to reach a range 90° and more, in addition, thereis a manipulability lowered near extreme positions. This limitationemerges by two reasons. Both there are collisions occurring between theplatform and the shank extending from the frame at extreme positionsnear 90° and the excessive number of 4 parallel arms is inadequate for asufficient distance from singular positions within all the work area.

The application of four parallel arms is insufficient in term ofutilization of the whole device's self-calibration feature and enhancedaccuracy of its positioning on the basis of unnecessary number ofmeasurements connected with the redundant number of arms with drives.Self-calibration feature is practicable but its achieved accuracy is nothigh.

An alternative mechanism with a parallel kinematic structure whichenables to reach a platform tilting angles range up to 90° is Octapod(Valá{hacek over (s)}ek, M., {hacek over (S)}ika, Z., Bauma, V.,Vampola, T.: The Innovative Potential of Redundantly Actuated PKM, In:Neugebauer, R.: Proc. of Parallel Kinematice Seminar 2004, IWU FhG,Chemnitz 2004, pp. 365-384) and Metrom (Schwaar, M., Jaehnert, T.,Ihlenfeldt, S.: Mechatronic Design, Experimental Properte Analysis andMachining Strategie for a 5-Strut-PKM, In: Neugebauer, R.: Proc. ofParallel Kinematice Seminar 2002, IWU FhG, Chemnitz 2002, pp. 671-681).Octapod's disadavantage is that arms are positioned all around theplatform. Metrom's disadavantage is lowering manipulability near extremepositions.

The aim of this invention is a device for a controlled spherical motionof bodies on the basis of mechanisms with a parallel kinematic structurewhich would achieve a moveability consonant to mechanisms with a serieskinematic structure, thereupon a range up to 200° in two rotations whilepreserving all advantages of mechanisms with a parallel kinematicstructure. Another goal of this invention is to achieve, at the sametime, a higher accuracy of a body's positions adjusting.

SUBJECT MATTER OF THE INVENTION

Subject matter of the device for a spherical motion of a body consistsin a fact that the shank connecting the body with the frame is sectionaland the spherical joint is arranged between the first part of the shankwhich is firmly fixed to the frame and the second part of the shankwhich is firmly fixed to the body while the number of parallel arms withdrives is excessive. An advantage is the number of parallel arms withdrives being at least five and a length of the shank part fixed to theframe being longer than a distance of the body's edge from a point wherethe shank part is fixed to the body.

Actuating parallel arms are fitted with the same drive or a combinationof telescopic, extensible continuous, traversable or rotational drives.

Alternatively, the actuating parallel arms are connected with the bodythrough an arm spherical joint and a body's shank.

As an advantage, the first part of the shank is fitted with a drive forchange of its length, its inclination, eventually for a modification ofthe spherical joint position. In the case of symmetrical arrangement ofthe actuating parallel arms and their number being six, there would bean advantage to extend them from three spots on the frame to three spotson the body. In a next alternative design, the actuating parallel armsare led from points on the frame obliquely into points on the body,whereas the top end of one actuating parallel arm is situated eventuallyabove the bottom end of an adjacent actuating parallel arm.

The advantage of this device consists in creation of the sectional shankwhich enables rotating the body by 90° and more without collisions withthe shank and in application of at least five redundant arms which allowto remove an occurrence of singular positions and to provide asufficient distance from them within all the work area of the body. Theapplication of at least five redundant arms with drives andadmeasurement, which is at least one more than it is necessarily neededfor self-calibration, enables to increase the accuracy substantially,and that both of the self-calibration itself and of a follow-uppositioning of the body in the work area.

SURVEY OF FIGURES ON DRAWINGS

The device for a body's spherical motion is schematically pictured inattached figures, where

FIG. 1 Represents an arrangement of the body connected to the frame byspherical joint and performing a controlled spherical motion with a helpof drives in parallel arms,

FIG. 2 Represents an arrangement of the body connected to the frame by aspherical joint and performing a controlled spherical motion with a helpof telescopic drives in parallel arms,

FIG. 3 Represents an arrangement of the body connected to the frame by aspherical joint and performing a controlled spherical motion with a helpof extensible continuous drives in parallel arms,

FIG. 4 Represents an arrangement of the body connected to the frame by aspherical joint and performing a controlled spherical motion with a helpof traversable drives in parallel arms,

FIG. 5 Represents an arrangement of the body connected to the frame by aspherical joint and performing a controlled spherical motion with a helpof rotational drives in parallel arms,

FIG. 6 Represents an arrangement of the body connected to the frame by aspherical joint which is, towards the moving body, positioned on a shankand performing a controlled spherical motion with a help of varioustypes of drives in parallel arms,

FIG. 7 Represents an arrangement of the body connected to the frame by aspherical joint, with a turning of the body by more than 90° from thebasic position,

FIG. 8 Demonstrates one of potential arrangements of actuating parallelarms in plan view,

FIG. 9 Demonstrates an arrangement of actuating parallel arms accordingto FIG. 8 in front view,

FIG. 10 Demonstrates one of other potential arrangements of actuatingparallel arms in plan view,

FIG. 11 Demonstrates an arrangement of actuating parallel arms accordingto FIG. 10 in front view,

FIG. 12 Represents a similar arrangement of the body connected to theframe by a spherical joint, with a turning of the body by more than 90°from the basic position, as it is evident in FIG. 7, though with analternative connection of the actuating parallel arms with the body.

FIG. 13 Represents an arrangement of the body connected to the frame bya spherical joint and through a withdrawable shank and

FIG. 14 Demonstrates another potential arrangement of actuating parallelarms in front view.

EXAMPLES OF THE DEVICE DESIGN

As it is evident in FIG. 1, body 1 is connected to frame 5 through ashank, the first part 9 of which is firmly fitted to frame 5 and itssecond part 10 is firmly fitted to body 1. The first part 9 of the shankcan eventually create one component together with frame 5 and the secondpart 10 may form one component with body 1. Both parts 9, 10 of theshank are together connected to spherical joint 2 which enables the body1 motion towards frame 5. Body 1 and frame 5 are connected to oneanother through parallel actuating arms 3 which are fitted with drives 4for draw-out movement of actuating arms 3. These parallel arms 3 withdraw-out drives 6 can be realized through working screws or telescopicworking screws, connected to the body and the frame with spherical oruniversal joints. The controlled spherical motion of body 1 is achievedby adapting the length of individual actuating arms 3. The number ofparallel arms 3 with drives 4 is redundant. It means, that the number ofparallel actuating arms 3 with drives is higher than the number ofdegrees of freedom of body 1, so that the number of parallel actuatingarms 3 is at least four. With regard to excluding singular positionsoccurrence in work area of the spherical motion of body 1, it isadvantageous when the number of parallel arms 3 with drives 4 is five atminimum. The application of minimally five additional parallel actuatingarms 3 allows to increase both the accuracy of self-calibration itselfand the follow-up accuracy of positioning body 1 in the work area.

The application of the sectional shank composed of the first and thesecond part 9 and 10 enables to turn body 1 by more than 90°. For thepurpose of such a turn, a length of the first part 9 of the shank fixedto frame 5 should be longer than a distance of the edge of body 1 from apoint where the second part 10 of the shank is fixed to body 1. Adaptingthe length of the second part of shank 10, a varied angle range ofrotating body 1 over 90° can be achieved.

The way of controlled rotating of body 1 with the help of actuatingparallel arms 3 is achieved through drives, with the help of whicheither the length of actuating parallel arms 3 is modified or theactuating parallel arms are rearranged with regard to frame 5, in caseof need it is possible to use a combination of various drives for thelength change or for a movement of actuating parallel arms 3. Thus, inFIG. 2, telescopic drives 6 are used to change the length of actuatingpositioning arms 3; in FIG. 3, extensible continuous drives 11 are usedto move actuating parallel arms 3 towards frame 5; in FIG. 4,traversable drives 7 are used to move bottom ends of actuating parallelarms 3 towards frame 5; in FIG. 5, rotational drives 8 are used forturning sectional actuating parallel arms 3 when extending or shorteningof particular distances between body 1 and frame 5 is achieved byturning individual parts of actuating parallel arms 3. In FIG. 6, therecan be evidently seen a possible use of above mentioned drive typescombination at one device, i.e. telescopic drive/s 6, combined withrotational drive/s 8 extensible continuous drive/s 11 and traversabledrive/s 7. A rotational joint may even be an intermediate joint of anactuating parallel arm connecting it with body 1 or a joint of anactuating parallel arm with body 1. There is an advantage of rotationaljoint 8 positioning on frame 5, so that the rotational drive weight neednot to be moved along by the arm's movement.

In FIG. 7, there can be evidently seen tilting of body 1 in a shape of aplane plate by more than 90° with regard to its basic horizontalposition, as it is demonstrated in pictures above. A drive type is notessential and also it is not limited to above mentioned drives.

Points of actuating parallel arms 3 connection both with frame 5 andwith body 1 are possible to be opted at random practically; asymmetrical arrangement of these points of connection is useful, as itis evident in plan view in FIG. 8 where there are 6 actuating parallelarms 3 with drives 4 used for body 1 spherical motion control, whereasthere are always top ends of adjoining actuating parallel arms 3connected by a joint and their bottom ends are connected with ends ofadjacent actuating parallel arms 3 on opposite sides. This arrangementof actuating parallel arms 3 is then showed in front view in FIG. 9. Asystem of actuating parallel arms 3 arranged in this way forms a nexusof six triangles.

A similar symmetrical arrangement of actuating parallel arms 3 and theirconnection with frame 5 and body 1 with a configuration according toFIGS. 8 and 9 is evident in FIG. 10, where can be evidently seen thatparticular ends of adjacent actuating parallel arms 3 are pointedtowards one another, though their connection with frame 5 and body 1 isnot situated in one conjoint place and points of connection areseparated from one another. In FIG. 11, there is the arrangement ofactuating parallel arms 3 according to FIG. 10 showed in front view.

One of other potential device designs with alternative junction ofactuating arms 3 with body 1 is shown in FIG. 12, which corresponds withthe device design in a tilted position according to FIG. 7, therewithclamping of actuating parallel arms 3 ends with body 1 is realized bymeans of shank 12 of body 1 and an arm's spherical joint 14 whichconnects shank 12 to actuating parallel arm 3.

In FIG. 13, there can be seen alternative configuration of the devicefor a body's spherical motion control where some part of the shankconnecting body 1 with frame 5 is fitted, except for spherical joint 2,with adjusting drive 13 which is arranged on the first part 9 of theshank here. Adjusting drive 13 serves for adjustment of spherical joint2 position, e.g. its distance from frame 5 and it is particularlyfavourable when using a device for control of a spherical motion ofreplaceable bodies 1 of different size, eventually depending upon a needof various extensions of body 1 deflection from its basic position.Adjusting drive 13 enables a better handling, too, eventually atransportation of the device.

FIG. 14 shows other possible arrangement of actuating parallel arms 3 infront view where actuating parallel arms 3 are guided symmetricallyalong the periphery of frame 5 and body 1, so that their bottom edgesare situated below top ends of adjoining actuating positioning arms 3.

1. A device for a body's spherical motion control connected with a frameby means of a spherical joint arranged on a shank connecting the bodywith the frame and through actuating arms with drives, demarcated by thefact, that the shank is sectional and the spherical joint is arrangedbetween the shank which is firmly fixed to the frame and the shank whichis firmly fixed to the body, whereas the number of parallel arms withdrives is redundant.
 2. A device for a body's spherical motion controlaccording to claim 1, demarcated by the fact, that the number ofparallel arms with drives is five at minimum.
 3. A device for a body'sspherical motion control according to claim 1, demarcated by the fact,that the length of the shank connected to the frame is longer than thedistance of the body's edge from the point of connection of the shank tothe body.
 4. A device for a body's spherical motion control according toclaim 1, demarcated by the fact, that parallel arms are fitted with atelescopic drive or an extensible continuous drive or a traversabledrive or a rotational drive.
 5. A device for a body's spherical motioncontrol according to claim 1, demarcated by the fact, that actuatingparallel arms are connected to the body through an arm's spherical jointand a shank of the body.
 6. A device for a body's spherical motioncontrol according to claim 1, demarcated by the fact, that the firstpart of the shank is fitted with a drive for a spherical joint positionchange.
 7. A device for a body's spherical motion control according toclaim 1, demarcated by the fact, that the number of parallel arms is sixand they are led from three points on the frame to three points on thebody.
 8. A device for a body's spherical motion control according toclaim 1, demarcated by the fact, that parallel arms are led from pointson the frame obliquely to points on the body.
 9. A device for a body'sspherical motion control according to claim 1, demarcated by the fact,that the top end of one parallel arm is situated above the bottom end ofan adjacent actuating parallel arm.
 10. A device for a body's sphericalmotion control according to claim 2, demarcated by the fact, that: thelength of the shank connected to the frame is longer than the distanceof the body's edge from the point of connection of the shank to thebody; parallel arms are fitted with a telescopic drive or an extensiblecontinuous drive or a traversable drive or a rotational drive; actuatingparallel arms are connected to the body through an arm's spherical jointand a shank of the body; the first part of the shank is fitted with adrive for a spherical joint position change; the number of parallel armsis six and they are led from three points on the frame to three pointson the body; and parallel arms are led from points on the frameobliquely to points on the body.